Regionality of short and long period oscillators in the suprachiasmatic nucleus and their manner of synchronization.

In mammals, the center of the circadian clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Many studies have suggested that there are multiple regions generating different circadian periods within the SCN, but the exact localization of the regions has not been elucidated. In this study, using a transgenic rat carrying a destabilized luciferase reporter gene driven by a regulatory element of Per2 gene (Per2::dLuc), we investigated the regional variation of period lengths in horizontal slices of the SCN. We revealed a distinct caudal medial region (short period region, SPR) and a rostro-lateral region (long period region, LPR) that generate circadian rhythms with periods shorter than and longer than 24 hours, respectively. We also found that the core region of the SCN marked by dense VIP (vasoactive intestinal peptide) mRNA-expressing neurons covered a part of LPR, and that the shell region of the SCN contains both SPR and the rest of the LPR. Furthermore, we observed how synchronization is achieved between regions generating distinct circadian periods in the SCN. We found that the longer circadian rhythm of the rostral region appears to entrain the circadian rhythm in the caudal region. Our findings clarify the localization of regionality of circadian periods and the mechanism by which the integrated circadian rhythm is formed in the SCN.

Transgenic rats expressing dominant negative BMAL1 showed circadian clock amplitude reduction and rapid recovery from jet lag.

The circadian rhythms are endogenous rhythms of about 24 h, and are driven by the circadian clock. The clock centre locates in the suprachiasmatic nucleus. Light signals from the retina shift the circadian rhythm in the suprachiasmatic nucleus, but there is a robust part of the suprachiasmatic nucleus that causes jet lag after an abrupt shift of the environmental lighting condition. To examine the effect of attenuated circadian rhythm on the duration of jet lag, we established a transgenic rat expressing BMAL1 dominant negative form under control by mouse Prnp-based transcriptional regulation cassette [BMAL1 DN (+)]. The transgenic rats became active earlier than controls, just after light offset. Compared to control rats, BMAL1 DN (+) rats showed smaller circadian rhythm amplitudes in both behavioural and Per2 promoter driven luciferase activity rhythms. A light pulse during the night resulted in a larger phase shift of behavioural rhythm. Furthermore, at an abrupt shift of the light-dark cycle, BMAL1 DN (+) rat showed faster entrainment to the new light-dark cycle compared to controls. The circadian rhythm has been regarded as a limit cycle phenomenon, and our results support the hypothesis that modification of the amplitude of the circadian limit cycle leads to alteration in the length of the phase shift.

Evaluation of symptoms and QOL with calcium alginate versus chitin-coated gauze for middle meatus packing after endoscopic sinus surgery.

OBJECTIVE: Nasal packing is used to control postoperative bleeding and wound healing, and it also exerts a very strong influence on the comfort of the patient. Sorbsan(®) (calcium alginate) is an absorbent packing that shows a potent hemostatic effect and is able to maintain wound surfaces in a moist environment by absorbing and gelling the wound exudate. The aim of this study was to evaluate the early symptoms and QOL with Sorbsan(®) versus Beschitin-F(®) (chitin-coated gauze) for middle meatus packing after endoscopic sinus surgery (ESS). METHODS: We performed a cohort study of 40 patients who underwent ESS. Following ESS, the patients were randomly allocated into two groups of 20 patients each who underwent insertion of either Sorbsan(®) or Beschitin-F(®) into the middle meatus. A daily diary was used to record the symptoms and QOL, measured using visual analogue scales, before the ESS and on each day thereafter. Postoperative bleeding and local infection were also recorded. RESULTS: The scores for each of the symptoms of nasal pain, headache, nasal bleeding and postnasal drip were statistically significantly lower in the Sorbsan(®) group. The scores for each of the QOL parameters, including the effect on their stay in the hospital and sleep disturbance, were also significantly lower in the Sorbsan(®) group. There were no findings of postoperative hemorrhage or local infection in either group. CONCLUSION: Sorbsan(®) packing did not cause any major complications and has the potential to reduce nasal pain and suffering in post ESS patients compared with gauze packing.